CPAP systems
A CPAP system includes a flow generator ( 10 ), a patient interface ( 50 ), an air delivery conduit ( 20 ) that interconnects the flow generator and the patient interface, wherein the air delivery conduit has an internal diameter of less than 19 mm. Preferably the air delivery conduit has an internal diameter of between about 10 mm and about 18 mm. The CPAP system may also include a controller for compensating for pressure swings and/or increased impedance within the system. Preferably the blower includes a low inertia blower.
1. A system comprising:
a flow generator including an outlet, a blower that supplies breathable gas at pressure to the outlet, a pressure sensor that measures a pressure of the gas supplied from the blower, and a flow sensor that measures a flow of the gas supplied from the blower;
an air delivery conduit coupled to the outlet of the flow generator; and
an air delivery control system configured to adjust a speed of the blower, at least in part, by:
estimating a pressure drop that will occur along the air delivery conduit;
determining a pressure set point from a predetermined therapy pressure and the estimated pressure drop that will occur along the air delivery conduit;
correcting a difference between the pressure set point and the pressure measured by the pressure sensor with a pressure controller loop;
determining a feedforward output from the flow measured by the flow sensor; and
adjusting an output of the pressure controller loop with the feedforward output.
2. The system of claim 1 , wherein the blower supplies the breathable gas at a pressure of 3-25 cmH2O.
3. The system of claim 2 , wherein the air delivery conduit includes a conduit portion having an internal diameter of between about 13 mm to about 16 mm.
4. The system of claim 3 , wherein the conduit portion has flexible spiral or helix ribbing with a pitch of about 4.5 to 5.5 mm that supports one or more heated wires.
5. The system of claim 3 , wherein the conduit portion is made from an integrated textile.
6. The system of claim 1 , wherein the air delivery conduit includes one or more heated wires.
7. The system of claim 1 , wherein the pressure controller loop is a proportional integral (PI) controller.
8. The system of claim 1 , wherein the pressure controller loop is a proportional integral derivative (PID) controller.
9. The system of claim 8 , wherein the flow measured by the flow sensor is filtered through a high pass filter prior to determining the feedforward output.
10. The system of claim 1 , wherein the feedforward output is further determined from a gain factor that is related to predicted pressure disturbances of one or more components of the system.
11. The system of claim 1 further comprising:
a patient interface, wherein the flow generator is coupled to a proximal end of the air delivery conduit, and wherein the patient interface is coupled to a distal end of the air delivery conduit.
12. The system of claim 1 further comprising: a recognition system configured to identify a type of the air delivery conduit, wherein the air delivery control system is configured to estimate the pressure drop that will occur along the air delivery conduit based on the type of the air delivery conduit identified by the recognition system.
13. A method comprising:
supplying, with a blower of a flow generator, breathable gas at pressure to an outlet of the flow generator;
measuring, with a pressure sensor of the flow generator, a pressure of the breathable gas supplied from the blower;
measuring, with a flow sensor of the flow generator, a flow of the breathable gas supplied from the blower;
adjusting, with an air delivery control system, a speed of the blower, at least in part, by:
estimating a pressure drop that will occur along an air delivery conduit coupled to the outlet of the flow generator;
determining a pressure set point from a predetermined therapy pressure and the estimated pressure drop that will occur along the air delivery conduit;
correcting a difference between the pressure set point and the pressure measured by the pressure sensor with a pressure controller loop;
determining a feedforward output from the flow measured by the flow sensor; and
adjusting an output of the pressure controller loop with the feedforward output.
14. The method of claim 13 , wherein the pressure controller loop is a proportional integral (PI) controller.
15. The method of claim 13 , wherein the pressure controller loop is a proportional integral derivative (PID) controller.
16. The method of claim 13 , wherein the feedforward output is further determined from a gain factor that is related to predicted pressure disturbances of one or more components of the system.
17. The method of claim 16 further comprising:
filtering the flow measured by the flow sensor through a high pass filter prior to determining the feedforward output.
18. The method of claim 13 further comprising:
delivering, with the air delivery conduit, the breathable gas supplied from the blower to a patient interface,
wherein the flow generator is coupled to a proximal end of the air delivery conduit, and wherein the patient interface is coupled to a distal end of the air delivery conduit.
19. The method of claim 18 further comprising:
heating, with one or more heated wires of the air delivery conduit, the breathable gas supplied from the blower.
20. The method of claim 13 further comprising:
identifying, with a recognition system, a type of the air delivery conduit,
wherein the pressure drop that will occur along the air delivery conduit is estimated based on the type of the air delivery conduit identified by the recognition system.